Editor’s Note: this is the seventh of eight biweekly columns in which the Department of Natural Resources Secretary will try to answer some of the many questions and concerns related to Chronic Wasting Disease (CWD) in Wisconsin.
“To say we’ve been on a steep learning curve with Chronic Wasting Disease would be a real understatement. I’ve said in earlier columns that we will learn and adapt as new knowledge about this disease is discovered. There are literally dozens of research efforts underway or planned to learn more. I don’t have enough room here to list everything, and there’s important research in the works that isn’t listed here. In this column, I’m going to try and give examples of the kinds of research underway. As always, if you have questions call us.”
Why is it that we still have so many questions about chronic wasting disease?
CWD is a difficult disease to study – it isn’t caused by bacteria or a virus that can be grown in a laboratory. In Wisconsin, it is affecting a wild population – the white-tailed deer — that every hunter knows has superb human avoidance skills. And, there’s a very long incubation period before an animal shows any signs of illness. Frankly, until it was found in Wisconsin, it was viewed as a local problem out west. Until recently, the scientists and wildlife managers who were attempting to learn more about it were hamstrung by small budgets and staff shortages – some of those problems continue but it’s getting better. It wasn’t until CWD jumped to Wisconsin that folks began clamoring for answers.
Who is working on CWD research in Wisconsin?
Researchers at the Department of Natural Resources, Department of Health and Family Services, University of Wisconsin, US Geological Survey and the Wisconsin Veterinary Diagnostic Laboratory are hot on the trail of new CWD knowledge. Efforts are underway in many areas including: prion biology; CWD transmission; susceptibility of other wildlife and domestic animal species to CWD; environmental contamination; how deer ecology affects CWD transmission and spread; human reactions to CWD; human health risks; CWD management and research techniques; and development and assessment of CWD diagnostic techniques.
By virtue of having a quantity of CWD positive deer tissues in the freezer, Wisconsin has become a major source samples for CWD research. We’ve been flooded with requests by researchers from other states and countries looking for positive tissue to conduct investigations into all aspects of spongiform encephalopathies – the family of diseases from which CWD comes.
Are there any results of this research that can help right away in Wisconsin’s work to control CWD?
Yes. And important ones, too. Results from the 42,000 deer tested last year have already given biologists practical new knowledge. For example, our partners at the USGS/University of Wisconsin Cooperative Wildlife Research Unit investigated the intensity of infection in different age and sex classes of deer harvested by hunters and found that infection rates generally increase with age and that by three to four years of age, bucks have infection rates twice as high as does. Also, USGS and DNR researchers have mapped where the CWD-positive and negative deer are and have identified “hot spots” of infection. Wildlife managers can how ask hunters to focus deer culling efforts on these hot spots to maximize out disease eradication efforts.
What kinds of research are being done in the field in the CWD affected area?
The range and variety of research underway is more than I can write about in just one column but I’ll try to give you a picture of some of what’s going on. As early as winter 2002, university researchers were live-trapping deer and fitting them with radio collars. Adult female deer form distinct social groups and researchers suspect that disease may be transmitted more rapidly within these social groups. The travels of these deer are tracked using the radio signals to learn more about how far deer of different sexes move and the amount of contact between animals within a social group and between different social groups. This is important to determine how quickly and how far CWD can spread within the deer herd. This effort would not be possible without the cooperation of area landowners allowing researchers to set up traps on their property. Thanks, folks.
Researchers are also using genetic markers to learn more about how CWD is transmitted within our deer herd. We’ll use muscle samples from deer removed by hunters from the area where the infection rate is highest to determine which deer are genetically related and whether animals are more likely to transmit disease within their social group. Results from this study will help determine if removal of social groups may be an improved strategy for reducing CWD transmission. There is a similar genetic study underway investigating the potential of CWD transmission among bucks and does during the fall breeding season.
We also plan to study what native wildlife scavenges deer carcasses under field conditions and what role scavengers might play in spreading the disease.
What kind of research is being done on how the disease spreads from animal to animal?
Recently University of Wisconsin researchers presented research findings showing that CWD prions can stick to clay soil types. Research like this will help us find the best ways to landfill CWD-affected deer carcasses and may eventually help us understand if the local environment can be contaminated by infected animals. Other University researchers working with deer in a contained laboratory setting have orally infected the deer with CWD. The scientists will track the disease as it progresses through the animals’ tissues and study which body fluids might be a source of disease to other deer.
A third study underway by the USGS/University Co-op unit and the DNR is studying the risks of disease transmission from baiting and feeding. Deer contact rates are being compared under natural browse conditions, unlimited feeding and restricted feeding. UW-Stevens Point plans to compare the effect of broadcast versus piled bait on deer interactions.
What about research on possible human health risks from CWD?
Over the next five years, the Department of Health and Family Services will be closely inspecting death certificates and medical charts, looking for possible links between CWD and deaths from the human prion disease, Cruetzfield-Jakob Disease (CJD). There is no evidence of a link between CWD and CJD at this time but we all realize that continued research on this important issue is needed.
What about research on improved CWD testing?
We took a big step forward recently when the scientists at the Wisconsin Veterinary Diagnostic Laboratory (WVDL) completed their comparison testing of new CWD tests. On the basis of this comparison study they have selected a new screening test that’s just as accurate but is faster with a reasonable cost. Test results should take about half the time they took last year, or about three to four weeks.
WVDL’s comparative study also identified that there may be other tissues of the body in addition to the lymph nodes of the head or the brain that can be used for CWD testing. Testing lymph nodes that lie under the skin may be a possibility for live animal testing – that would be very useful to the captive wildlife industry and to field researchers.
Learn and adapt
I’ve said before that as we learn more about CWD we’ll adapt our management strategy to reflect that new knowledge. We are and will continue to incorporate findings from research like the projects I’ve mentioned here into our CWD management. If there’s a better way to whip CWD, you can bet I’ll be leading the charge.
We’re also looking to learn more about the effect of this effort on you, the folks that live and hunt in the infected area. Our sociologists will be interviewing hunters and landowners on both sides of this issue as part a seven-state effort to survey citizens’ attitudes and beliefs on CWD management.
Many of you may already have been visited by one of our biologists in a door to door visitation effort we’re making in the intensive harvest zone. We’re visiting you to listen, to answer your questions and put a “face” on the people asking you to help us with the tough job of controlling CWD. Thanks for everything you’re doing to help.